It's not a forced method, its an option. In my experience setting up my own Login.gov account, and helping family members with theirs, the online methods have frequent and frustrating technical difficulties. This option may be preferable than spending an hour or two trying to get the Login.gov mobile website to actually use your device's camera.
I haven't actually used the system in question; I'm just speculating based on my frustration with the increasing number of banking, trading, and even taxi booking apps that will refuse to work on modified phones.
